SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f86200e0fa970572858e0f2fe0848afc635deadffa3d25eee73943121d4e48c' 
  AND token = 'AMXnrZLUEGTbji1r8wUIBXuuDecxXpYaapRZgIoNeag=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}